Systems and methods for precise radio frequency localization of wireless nodes using time difference of arrival and decoupling in time synchronizing of the wireless nodes from ranging

ABSTRACT

In one embodiment, an asynchronous wireless system for localization of nodes comprises a first wireless node being configured to receive a first communication from a third wireless node having an unknown location, to determine time difference of arrival (TDoA) information of the reception of the first communication between each of the first and a second wireless node, to determine TDoA ranging including a relative or absolute position of the third wireless node using the time difference of arrival information, and to synchronize the first and second wireless nodes based on a second communication with the synchronization being decoupled in time from the first communication. In another embodiment, a computer implemented method comprises receiving, with first and second wireless anchor nodes, packets from a wireless arbitrary device and performing time difference of arrival ranging upon reception of the packets between each of the first and the second wireless anchor nodes.

RELATED APPLICATIONS

This application is related to U.S. Pat. Nos. 10,568,064, 10,660,060,10,772,067, 10,757,675, and U.S. application Ser. No. 16/283,465, whichare incorporated by reference herein.

FIELD

Embodiments of the invention pertain to systems and methods for preciseradio frequency localization using time difference of arrivalinformation and also decoupling synchronization of wireless nodes fromthe ranging.

BACKGROUND

In the consumer electronics and computer industries, wireless sensornetworks have been studied for many years. In archetypal wireless sensornetworks, one or more sensors are implemented in conjunction with aradio to enable wireless collection of data from one or more sensornodes deployed within a network. Each sensor node may include one ormore sensors, and will include a radio and a power source for poweringthe operation of the sensor node. Location detection of nodes in indoorwireless networks is useful and important in many applications.

Localization based on time difference of arrival (TDoA) technique formultilateration is performed using radio frequency measurements fordetermining location of wirelessly equipped objects in three dimensionalspace. RF-based localization may be performed in numerous ways. Anexemplary implementation includes a hub and multiple sensor nodes. Notethat the hub may be replaced with a node, or indeed, one or more of thenodes may be replaced with a hub. Distances are estimated using radiofrequency techniques between all the individual pairs via RFcommunications. In TDoA, one node transmits a signal. Multiple othernodes receive the signal, either by directly receiving it as a target ofthe communication or by sniffing the communications between other pairsof nodes, and the time difference between reception at each receive nodeis calculated. TDoA requires synchronization of the receivers of thenodes to accurately measure the difference in receive times. This can bedone by operating all of the receivers on a shared clock and comparingabsolute timestamps. In wireless systems where a shared clock is notavailable, the receivers must be synchronized in another way. Thesynchronization may be coupled to the TDoA operation, or may bemaintained as an independent operation, since synchronization may notneed to be performed frequently in situations when the individual clocksare relatively stable. Additionally, various estimations must beperformed to use the RF communications to estimate the RF signal traveltimes and hence distances between the various nodes. This can beperformed in various ways, including using estimations of the variouschannel states between the nodes.

SUMMARY

Embodiments of the invention pertain to wireless systems having wirelessnodes and methods for precise radio frequency localization using timedifference of arrival information. Synchronization of wireless nodes isdecoupled from the localization. In one embodiment, an asynchronouswireless system for localization of nodes in a wireless networkarchitecture comprises first and second wireless nodes with at least onewireless node having a known location and including a wireless devicewith one or more processing units and RF circuitry for transmitting andreceiving communications in the wireless network architecture and athird wireless node having an unknown location and including a wirelessdevice with RF circuitry to enable communications with the first and thesecond wireless nodes in the wireless network architecture. The one ormore processing units of the first wireless node are configured toexecute instructions to receive a first communication from the thirdwireless node, to determine time difference of arrival (TDoA)information of the reception of the first communication between each ofthe first and the second wireless nodes, to determine TDoA rangingincluding a relative or absolute position of the third wireless nodeusing the time difference of arrival information, to send a secondcommunication with a synchronization packet received by the secondwireless node, and to synchronize the first and second wireless nodesbased on the second communication with the synchronization of the firstand second wireless nodes being decoupled in time from the firstcommunication.

In another embodiment, a computer implemented method for localization ofa wireless arbitrary device in a wireless network architecture,comprises initializing the wireless network architecture having firstand second wireless anchor nodes and a plurality of wireless sensornodes, preparing, with the plurality of wireless anchor nodes, forlocalization of the wireless arbitrary device that performs wirelesslocal area network (WLAN) active scanning or maintains a WLANassociation to any node. The method further includes receiving, with thefirst and second wireless anchor nodes, packets from the wirelessarbitrary device and performing time difference of arrival (TDoA)ranging upon reception of the packets between each of the first and thesecond wireless anchor nodes.

Other features and advantages of embodiments of the present inventionwill be apparent from the accompanying drawings and from the detaileddescription that follows below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an archetypical example of a use of time difference ofarrival to determine the location of an object.

FIG. 2 illustrates a timing diagram for communications of the wirelesssystem 100.

FIG. 3A illustrates a wireless architecture for synchronization ofwireless nodes while FIG. 3B illustrates a decoupling in time of theTDoA ranging from the synchronization in accordance with one embodiment.

FIG. 3C illustrates a wireless architecture of wireless nodes in anotherembodiment in which other nodes (e.g., node 408 (N408)) have directcommunication (e.g., 445, 448) with the node N440.

FIG. 4A illustrates implementation of a TDoA wireless system inaccordance with another embodiment.

FIG. 4B shows a timing diagram for the TDoA wireless system inaccordance with another embodiment.

FIGS. 5A-5C illustrate a method for performing a TDoA ranging forlocalization in accordance with another embodiment.

FIGS. 6A-6B illustrates a method for monitoring a tracker device in aWiFi context in accordance with one embodiment.

FIG. 7 illustrates a wireless system with arbitrary anchors to locate atracker device in accordance with one embodiment.

FIG. 8 illustrates an anchor free method for localization of wirelessdevices of a wireless sensor network in accordance with one embodiment.

FIG. 9A shows an exemplary embodiment of a hub implemented as an overlay1500 for an electrical power outlet in accordance with one embodiment.

FIG. 9B shows an exemplary embodiment of an exploded view of a blockdiagram of a hub implemented as an overlay for an electrical poweroutlet in accordance with one embodiment.

FIG. 10A shows an exemplary embodiment of a hub implemented as a cardfor deployment in a computer system, appliance, or communication hub inaccordance with one embodiment.

FIG. 10B shows an exemplary embodiment of a block diagram of a hub 964implemented as a card for deployment in a computer system, appliance, orcommunication hub in accordance with one embodiment.

FIG. 10C shows an exemplary embodiment of a hub implemented within anappliance (e.g., smart washing machine, smart refrigerator, smartthermostat, other smart appliances, etc.) in accordance with oneembodiment.

FIG. 10D shows an exemplary embodiment of an exploded view of a blockdiagram of a hub 1684 implemented within an appliance (e.g., smartwashing machine, smart refrigerator, smart thermostat, other smartappliances, etc.) in accordance with one embodiment.

FIG. 11 illustrates a block diagram of a sensor node in accordance withone embodiment.

FIG. 12 illustrates a block diagram of a system or appliance 1800 havinga hub in accordance with one embodiment.

DETAILED DESCRIPTION

Systems and methods for determining location of wireless sensor nodesusing radio frequency communications between the nodes and variousRF-enabled devices are described herein. Time difference of arrival iscombined with techniques to mitigate the effect of multipath issues andto overcome sampling and synchronization limitations to facilitatehighly precise determination of location.

In various applications of wireless sensor networks, it may be desirableto determine the location of sensor nodes within the network. Forexample, in wireless sensor networks, knowledge of location can addcontext to sensed data. In one example, knowledge of location intemperature sensing networks can enable mapping of temperaturevariations. Thus, it is desirable for systems and methods to enablelocation detection of nodes in wireless networks. Determination oflocation may be used to facilitate such applications as asset tracking,location context-based marketing and information, indoor navigation, andimproved connectivity provisioning and configuration. While GPS deliversreasonable location services in clear outdoor environments, indoorlocation services remain inadequate today.

RF-based location services typically make use of one or more RFtransceivers in known locations (often called “anchors”) and a targetobject with an unknown location that is to be determined. RFcommunications are performed between the anchors and the target objectand the location is determined based on these communications. Theoverall process is typically described in two operations—ranging andtriangulation. In the ranging operation, RF communication is performedbetween an anchor and the object to determine the distance between theanchor and the object. This is repeated for multiple anchors to obtain aset of ranges. These are then used in the triangulation operation todetermine the position of the object in three dimensional space.Typically, sufficient anchors are used to allow for some error reductionthrough redundancy in the triangulation process. The overall process istherefore based on the time of arrival between the object and thevarious anchors. In an alternate methodology, rather than requiringindividual communications between the object and the various anchors,time difference of arrival may be used. In this approach, directcommunication occurs between the object and one master anchor or with athird party device. These communications are also received by otherdevices (e.g., anchor devices), called sniffers, with known or estimatedrelative positions to the master. The differences in time of arrival ofthe communications at the various sniffers, the master, and the objectcan then be used to estimate the location of the object. This has theadvantage of reducing the number of overall communications needed. Itmay also exploit existing communication (e.g., standard WiFi associationand communication packets) without requiring significant alteration oraugmentation of the communication methodology. Any of the wireless nodesdescribed herein can be part of a wireless network architecture that isused for localization or can be third party devices that alsocommunicate with the wireless network architecture.

The accuracy of a location service is typically provided as a numericalmeasure of the position as determined by the service versus the actualphysical location. In particular, location services in indoorenvironments are often prone to outliers, where a few locationdeterminations may be significantly erroneous, despite the fact thatmany measurements deliver good accuracy. As a consequence, while aquoted numerical accuracy may appear to be sufficient for a givenapplication, in fact, the outliers may make the effective reliability ofthe localization so poor as to be unusable in practice.

Depending on the application, the time to achieve location estimationmay be an important parameter as well. For example, real time indoornavigation services may require responsiveness of a single second orless to enable accurate navigation guidance. Asset tracking orcontext-based services, on the other hand, may be provided with slowerlocation services.

The range of a location service describes the maximum distance overwhich location can be determined. In an RF-based location system, thischaracterizes the maximum separation between the minimum number ofanchors to achieve location service functionality and also theseparation between these anchors and the target object to be located.Obviously, the greater the range, the more sparse the locationinfrastructure requirements, reducing cost of deployment.

Indoor environments are typically difficult environments for RF-basedlocation services. In particular, the ranging or angle determinationprocess that is used as the first operation in localization isparticularly sensitive to reflections that commonly exist in indoorenvironments. These reflections result in multiple paths forming for theRF signal to propagate between the communicating radios on the anchor(s)and the object. This so-called multipath problem can result in erroneousdetermination of signal strength, range or angle. For example, if a paththat includes a reflection is misidentified as the range between ananchor and the object, it results in an overestimation of the rangeversus a direct path. This can then result in errors in triangulation.Indoor location services are highly prone to these multipath effects,leading to outliers, where certain locations result in very largeerrors. Any robust indoor location service must correctly deal withthese multipath effects to deliver good accuracy with minimal outliers.

In addition to multipath effects, attenuation of signals can be aserious problem as well. RF signals are generally attenuated morestrongly in indoor environments due to absorption of signals by walls,etc. This in turn can directly introduce error in the measurements, or,at the very least, can reduce the effective range of the system,necessitating the use of more anchors. If the anchor cost is high, thiscan significantly impact cost of deployment.

Finally, the overall cost of deployment can be a serious challenge.Given the range and multipath concerns with indoor environments,multiple anchors are commonly needed to provide adequate errorcorrection and provide sufficient indoor coverage given the increasedattenuation. Should these anchors require expensive hardware that issolely dedicated for location service provision, this can make thesolution non-viable for cost of deployment reasons alone.

Exemplar prior indoor localization technologies can be subdivided into afew main categories based on their choice of frequency/protocol. Theseinclude those based on 2.4 GHz ZigBee solutions, those based on 2.4 GHzBluetooth solutions, those based on WiFi (e.g., sub GHz, 2.4 GHz, 5 GHz,6 GHz) and those based on Ultra-wide band (UWB) at >5 GHz. In additionto categorization based on frequency/protocol, such technologies canalso be characterized based on their method of position determination.Position determination is typically achieved, for example, using one ormore of signal strength (RSSI), angle of arrival (AOA), time of arrival(TOA), or time difference of arrival (TDoA).

In Time of arrival (TOA) and time difference of arrival (TDoA) systems,the time for a signal to propagate from a transmitter to a receiver (orto a master and sniffers for TDoA) is used to estimate distance betweenthe same. Since the speed of propagation is relatively fixed, suchsystems are much more robust than RSSI-based systems, and also do notrequire the antenna sophistication of AOA systems. On the other hand,such systems too are susceptible to multipath effects, since a dominantreflected signal will have a longer time of arrival that a weaker directpath, and, if selected as the distance, may cause significant error inthe position calculation. Additionally, since time is the measuredparameter, such systems are heavily affected by the sampling clockaccuracy of the time measurement system, and also show a strongdependence on the signal bandwidth; wider bandwidth systems typicallyshow much better multipath tolerance, reduced outliers, and overallimproved accuracy.

Location information may be used to estimate the relative position ofsensors such as security cameras, motion sensors, temperature sensors,and other such sensors as would be apparent to one of ordinary skill inthe art. This information may then be used to produce augmentedinformation such as maps of temperature, motion paths, and multi-viewimage captures. Therefore, localization systems and methods are desiredto enable accurate, low-power, and context-aware localization of nodesin wireless networks, particularly in indoor environments. For thepurpose of this, indoor environments are also assumed to includenear-indoor environments such as in the region around building and otherstructures, where similar issues (e.g., presence of nearby walls, etc.)may be present.

U.S. Pat. No. 10,568,064, which is incorporated by reference herein,discloses various systems and methods for using time difference ofarrival to estimate the location of an object. FIG. 1 illustrates awireless system for localization of nodes utilizing time difference ofarrival information. The wireless system 100 is configured to have onemaster node 410 (M410), one node 440 at unknown location (N440), andsniff nodes (e.g., S420, S430, etc.). FIG. 1 shows an archetypicalexample of a use of time difference of arrival to determine the locationof an object.

Here, N440 represents the object to be detected. This is often referredto as a tracker (or tracker device). There are 3 devices with knownlocations shown, M410, S420, and S430. M is used to denote a master,which handles the direct communications with the node N440. S is used todenote sniffers, which do not explicitly communicate with the node N440but listen to the communications between the node N440 and the masterM410. Bidirectional communication is established between N440 and M410,as denoted by 441 and 412. This communication was used to determine thedistance between N440 and M410 using various possible techniques toestimate an accurate transit time between the same. Various suchtechniques are disclosed in U.S. Pat. No. 10,757,675 and U.S. patentapplication Ser. No. 16/283,465 and can be applied here, as would beapparent to one of ordinary skill in the art. In TDoA, the absolutedistance between N440 and M410 does not necessarily get directlycalculated. The data can be combined to determine the final location.The communication from the node N440 was also sniffed by the sniffers,as represented by communications 442 and 443. Anchor synchronization isneeded to enable determination of the various transit times. This isachieved by synchronization communication 402 and 404 (and also 412between M410 and N440) between M410 and S420 and S430 respectively.Using the various extracted timing, the transit times between the nodeand the various anchors M410, S420, and S430 can be determined.Additional anchors can also participate, as would be apparent to one ofordinary skill in the art. If the location of some or all of the anchorsis known, or the relative positions are known, then the absolute orrelative position of the node can be calculated through a triangulationprocess. Various methods to achieve this are disclosed in U.S. Pat. No.10,757,675 and U.S. patent application Ser. No. 16/283,465 and can beapplied herein, as would be apparent to one of ordinary skill in theart.

For example, based on two transmit and receive time stamps between twowireless nodes, an average time of flight between these nodes can beestimated. This process can be repeated multiple times and at multiplefrequencies to improve precision and to eliminate or reduce degradationdue to poor channel quality at a specific frequency. A set of pathlengths can be estimated by repeating this process for various nodepairs. Then, by using a geometric model, the relative position ofindividual nodes can be estimated based on a triangulation-like process.

This triangulation process is not feasible in a tree-like network, sinceonly path lengths between any node and a hub can be measured. This thenlimits localization capability of a tree network. To preserve the energybenefits of a tree network while allowing localization, in oneembodiment of this invention, a tree network for communication iscombined with mesh-like network functionality for localization. Oncelocalization is complete with mesh-like network functionality, thenetwork switches back to tree-like communication only and only time offlights between the nodes and the hub are measured periodically.Provided these time of flights are held relatively constant, the networkthen assumes nodes have not moved and does not waste energy attemptingto re-run mesh-based localization. On the other hand, when a change inpath length in the tree network is detected, the network switches to amesh-based system in combination with tree-like network andre-triangulates to determine location of each node in the network.

In one embodiment, a Location Algorithm includes anchor-basedTriangulation. In an anchor-based system, the location of anchor nodes(e.g., hubs, sensors, devices, etc.) is known. The unknown location ofother devices is calculated based on the known location of the anchorsas well as the measured distance between each device and each anchor.The location of these unknown devices is calculated one by one with thesame procedure. For each of the devices, the distance di to anchor i is:

(t _(i)-t _(tracker))c=d _(t)=√{square root over ((x-x _(i))²+(y-y_(i))²+(z-z _(i))² +n _(i))}

where x_(i), y_(i), and z_(i) are the coordinates of the ith anchor;t_(i) is the receive time stamp, c is the speed of light, ; x, y, z andt_(tracker) are the coordinates and the transmit time of the unknowndevice, which is the goal of the estimation. By setting up a differenterror function, ni(x, y, z, x_(i), y_(i), z_(i)), for the distancemeasurement, one can use least square errors to estimate the location ofthe unknown device (x,y,z).

In another embodiment, for an Anchor-less Triangulation setup, there isno known location for any of the devices. The algorithm has to use thedistance measurement between pairs of the devices to determine therelative location of each device. The goal is to find out the relativelocation of all devices to minimize the overall error of the distancemeasurement. There are multiple types of algorithms including anincremental algorithm and a concurrent algorithm. An incrementalalgorithm starts with a small set of devices and calculates theirlocations based on distance measurement. The small set of devices isthen used as anchor nodes for other devices. It is a simple algorithmbut with the drawback that the error in early calculated nodes can beeasily propagated to the later nodes, even with an advanced algorithmwhich updates location of the early nodes.

A concurrent algorithm solves the issue of the incremental algorithm dueto the concurrent algorithm estimating all locations at the same time toachieve a global optimum with lower error than incremental algorithm. Itusually uses iterative process to update the location of the devices,therefore it will take a longer time to converge while using morecomputation power and memory.

FIG. 2 illustrates a timing diagram for communications of the wirelesssystem 100. The unknown node N440 can initiate the packet transaction.N440 sends a communication 441 (e.g., forward packet 441) to the master(M) node 410 at time T₁. The master node 410 receives the communication441 at time T₂. The master node 410 responds with a communication 412(e.g., an acknowledgement packet 412) at time T5. The sniff nodes 420and 430 listen to the communications 442-443 at times T₄ and T₃ (e.g.,forward packets 442-443) from N440 and the communications 402 and 404(e.g., acknowledgement packet 402 and 404) from the master node 410. Thesniff node 420 receives the communication 443 at time T₃ and receivesthe communication 402 at time T₆. The sniff node 430 receives thecommunication 442 at time T4 and receives the communication 404 at timeT₇. The received packets 441-443 originate from the same communicationfrom N440.

The TDoA is now calculated based on the arrival of the forward packetsat the master and sniff nodes from N440. The packet transmission time ofthe acknowledgement packets from the master node is now used to alignthe timing between the nodes in accordance with Equation 1 below withdelta offset equaling T₆-T₅- T_(oF) M410-S420:

$\begin{matrix}{T_{{DoAM}410 - S420} = {T_{2} - T_{3}^{M410}}} \\{= \begin{matrix}{T_{2} - T_{3} - {{delta}{offset}{between}}} \\{{clocks}{of}M410{and}S420}\end{matrix}} \\{= {( {T_{2} - T_{3}} ) + T_{6} - T_{5} - T_{{oFM}410 - S420}}} \\{= \begin{matrix}{( {T_{2{sampling}} +_{T2{frac}}{- T_{3{sampling}}} - T_{3{frac}}} ) + T_{6{sampling}} +} \\{T_{6{frac}} - T_{5{sampling}} - T_{5{frac}} - T_{{oFM}410 - S420}}\end{matrix}}\end{matrix}$

In one embodiment of the present invention, some or all of thesynchronization transactions (e.g., communications 402, 404) can bedecoupled from the ranging transactions (e.g., communications 441, 412,442, 443). For example, since resynchronization may be needed relativelyinfrequently compared to the temporal need for ranging, the transactionsthat include communications 402 and 404 may be used only occasionally.This reduces network congestion and allows the ranging to be performedfaster due to less frequent synchronization.

In another embodiment of the present invention, the node N440 may notdirectly communicate with the master M410, i.e., there may be othernodes (e.g., node 408 (N408)) involved that have direct communication(e.g., 445, 448) with the node N440 as illustrated in FIG. 3C, and themaster may only be responsible for synchronization and direction of theoverall system as illustrated in FIG. 3A.

FIGS. 3A and 3B show an embodiment of a system where the timesynchronization is decoupled from the ranging measurements. In thiscase, the communication to N440 to trigger its outbound communication(e.g., communication 441-443) may come directly from M410 or mayoriginate from S420, S430 or indeed, any other wireless device (e.g.,N408) that is configured to participate. Alternatively, N440 may be“triggered” by internal sources, such as timers or sensors (e.g., motionsensor).

The decoupling of the TDoA ranging (FIG. 3B) from the synchronization(FIG. 3A) allows significant flexibility in the overall configuration ofthe wireless architecture and communication strategy, with variousadvantages based on the embodiment. FIG. 3A shows an archetypalimplementation of synchronization transactions between a master M410 andsniffers S420 and S430. There may be additional sniffers, as would beapparent to one of ordinary skill in the art.

For achieving synchronization between M410 and sniffers S420, S430, timeof transmission (TX) and reception (RX) timestamps and channel stateinformation (CSI) are captured on synchronization (or herein afterreferred to as “sync”) packets of communication 402 and 404 and are usedto determine clock drift, using time determination techniques asdescribed in U.S. Pat. No. 10,757,675 and U.S. patent application Ser.No. 16/283,465, or other such techniques as would be apparent to one ofordinary skill in the art. In the new method of synchronization, asynchronization packet sent by one or more devices (that may or may notbe a master) is received by the sniffers S420, S430 and is used tocorrect for the phase/frequency offset between the nodes. Thissynchronization packet can be an explicit synchronization packet or canjust be an acknowledgement to a packet sent from the mobile node to oneof the other nodes. Absolute phase difference at the time of sync andthe rate of change of the phase difference is used to interpolate to thephase difference at the time of TDoA.

Anchor clocks are often reasonably stable, so synchronization can bedone less frequently than ranging measurements yet still maintainbenefits of many redundant sync measurements under different channelconditions; sync can also apply to multiple trackers. Additionally, inthe case where anchor coordinates are known, direct ranging betweenanchors is not required and synchronization may be achieved using theknown locations.

In another embodiment, a TDoA system utilizing known anchor locationsmay be implemented. Aspects of this are illustrated in FIG. 4A. In FIG.4A, the master node 460 is a wireless device that receives forwarddirection multicarrier packets and transmits backward directionmulticarrier packets. In one example, the sniffer node 470 is a wirelessdevice that only receives unidirectional or broadcast multicarrierpackets in this context, and the tracker is a wireless device 480 thattransmits forward direction multicarrier packets. The line-of-sightsignal travel time between the master node 460 and the sniffer node 470is defined as t ms 462. The signal travel times from the tracker 480 arenot known and the TDoA operation is used to estimate signal travel timesto the sniffer and to the master as t_ts 465 and t_tm[k-1] 494 andt_tm[k] 463, respectively. In case of multipath channel conditions thereis more than one estimate candidate.

When the tracker 480 transmits a forward packet, the master node 460receives the forward (FW) packet and starts filling its multicarriertraining symbol with known content (e.g., WiFi long training field(LTF)) into a buffer (e.g., FFT buffer for FFT analysis) at clock cyclem_fw_t as showing in timing diagram 500 of FIG. 4B. The timing diagram490 shows timing for packets received at the master node with timingdiagrams 491, 492 and packets received at the sniffer node with timingdiagram 493. The sniffer 470 receives the same packet and starts fillingthe LTF into a buffer (e.g., FFT buffer for FFT analysis) at clock cyclesn_fw_t. When the master node 460 transmits a backward packet with itsLTF starting at time m_bw_t then the sniffer receives it and startsfilling the LTF into its FFT buffer at clock cycle s_bw_t. Due to thediscrete nature of the clock and the inaccuracy of packet detection, thereceiver clock time stamps do not align with the actual start of thesymbol. Thus, any ranging methods based solely on these time stamps willbe inferior compared to the techniques introduced here. All the timestamps are based on the receivers' own clocks and the sniffer clockdiffers from the master node clock by time varying offset phi(t). Thesniffer receiver measures and reports a frequency offset that can betranslated into the rate, m, at which phi(t) is changing. The clockoffset typically follows linear behavior phi(t)=m·t+phi_0 if the offsetmeasurement is done frequently enough.

For symbol equalization purposes the master node estimates the forwardfrequency domain channel from the training symbols as channel stateinformation csi_m_fw and the sniffer as csi_s_fw. The sniffer estimatesthe backward channel as csi_s_bw. These channel estimates can alsoinclude the transmitter and receiver involved. Since transceivers canhave hundreds of nanoseconds delay, and we are only interested in timeof flight over the air, it is preferred to remove any known transceiverresponse by, e.g., dividing the channel response by the transceiverresponse. One way to measure the transceiver response is to feed backthe signal from the transmitter to the receiver and save that channelstate information. The determined sorted delay values of time domainversions of those channels are defined as m_fw_d[], s_fw_d[] ands_bw_d[], respectively. Examples of methods for creating these timedomain channel vectors can include FFT, Matrix Pencil, SparseApproximation, MUSIC, as discussed in US patent application No.16/283,465, 10,757,675, and other such techniques as would be apparentto one of ordinary skill in the art. In one embodiment, the vectors maybe shortened to length k and j as m_fw_d[i m_fw-k, i_m_fw-k+1 . . .,i_m_fw], s_fw_d[i_s_fw-k, i_s_fw-k+1 . . . ,i_s_fw] ands_bw_d[i_s_bw-j, i_s_bw-j+1 . . . ,i_s_bw], where i_m_fw, i_s_fw andi_s_bw are the indices of the strongest paths.

A set of phi estimates are defined as phi=t_ms-s_bw_t+m_bw_t-s_bw_d[].Since we know that phi(t)=m·t+phi_0 then it is possible to pick whichs_bw_d[] items have a match (e.g., match best) with the extrapolated phifrom the historical data. This can potentially lower the count, j, evendown to one (i.e., provide a unique solution).

If the channel between the master and the sniffer is unknown, in oneembodiment, it is possible to proceed as follows:

It is possible to estimate k.j signal travel time candidates fromtracker to sniffer as t_ts[]=s_fw_t+s_fw_d[]⊕s_bw_d[]+t_ms+s_bw_t·(m-1)−m_bw_t−t_sn(state_s), where ⊕-operatorcreates a vector with all k·j sums of every possible path delaycombinations. For example, in f=x⊕y,f[i]=x[mod(i,len(x))]+y[mod(I,len(x))+floor(i/len(x)]. t_sn is a knownadditional delay in the sniffer receiver caused by gain etc statechanges.

Then, k signal travel time candidates from tracker to master may beestimated as t_tm[]=m_fw_t+m_fw_d[]−trx_m(state_m), where trx_m(state)is a known combined delay of the master transmitter and receiver. If thefull transceiver response is known and corrected in the channel stateinformation (csi_m_fw, csi_s_fw and csi_s_bw) then only the additionaldelay due to gain etc state change is applied.

Finally, j·k{circumflex over ( )}2 travel time difference candidates maybe estimated as t_ts[] ⊕ (-t_tm[]). These candidates can be used in TDoAmultilateration.

If there is a known master-sniffer channel, then, in one embodiment, itis possible to proceed as follows:

It is possible to define phi(t) with linear equation m·t+phi_0. If thechannel, csi_ms, between the master and sniffer is known then it ispossible to define the ratio csi_s_bw/csi_ms as a circle that goesaround origin r times. For signal with bandwidth of BW, it is possibleto model phi(t) as m_bw_t-s_bw_t-r/BW for various packets and thenestimate m and phi_0. Alternatively, m is also available from thesniffer receiver.

Then, to implement TDoA ranging, it is possible to estimate k signaltravel time candidates from tracker to sniffer asts_t[]=s_fw_t+d_s_fw[]+phi_0+m·m_bw_t. It is further possible toestimate k signal travel time candidates from tracker to master astm_t[]=m_fw_t+d_m_fw[]. Finally, it is possible to estimate 102 traveltime difference candidates as ts_t[] ⊕(-tm_t[]). These candidates can beused in TDOA multilateration.

It is usually beneficial to have as few travel time candidates aspossible. If the location of the tracker is known to be within a certainphysical space (i.e., a building), then the travel times have an upperand lower limit that can be calculated when the anchor locations areknown. Any travel time candidate that is outside of these limits can besafely removed.

There are typically two (or more) locations that would give the samedifferential distance measurements. Many of the TDOA multilaterationmethods return both these locations as well as the transmit time of theforward packet (or clock offset between the master and the tracker).Some examples of multilateration methods are exhaustive search,Gauss-Newton, various closed form solutions or combination of those. Ifboth locations are within the physical space where the tracker is knownto be, then the correct location can be chosen by checking that thetransmit time matches with the master location, tracker location and anyknown master receiver delay.

When more than one travel time candidate is used in multilateration thenit is possible to give them weighting based on any a priori knowledge ofthe reliability of that candidate. This weight can be based on e.g. howfar (in distance or index) the candidate path is from the strongestpath, the path strength, the path distance, signal strength or anchorstatistics. Many algebraic multilateration methods can add the weightthrough a matrix multiplication. In an exhaustive search method, theweight can also be made location specific. This can reduce sensitivityto the travel time estimation outliers that many Least Square Errorsolutions suffer from. It also allows taking into account any knowngeometry of the space, radio signal blockers or reflectors.

Sometimes the tracker can use multiple antennas either by switchingbetween them or transmitting from both with intentional delay added toone. If multiple receive packets are averaged for noise reduction, thenthese cases must be identified first. In case of antenna switching, onlypackets from the same antenna can be averaged due to the channeldifferences between the antennas. If one antenna performs better thanthe other (based on signal to noise ratio, signal strength etc.) thenthe better antenna can be used instead of both. In case of one delayedantenna, the packets may need to be time aligned before averaging incase the receiver started sampling them from different parts of thepacket. Also, in one example, any added antenna delay must be removedfrom the travel time estimates before multilateration.

Multiple anchors may transmit synchronization packets. In such anembodiment, there may be no need to designate a single anchor as the“master” (transmitting) role and the role of global timing referencemanagement may change between the various anchors in an arbitrary manneror as needed by the application. In one embodiment, the choice of mastermay rotate based on the expectation of strongest signal strength orquality of communication based on past transactions and/or estimates ofmotion and/or location of the object being tracked.

In another embodiment, ranging activity may be used to trigger more syncinteractions, in a loose coupling such that synchronization is triggeredas needed.

In the ranging transactions as used in TDoA, Tracker (N440) can transmitany multicarrier (e.g., OFDM) packet to any destination address (e.g., aWiFi access point); nearby anchors will receive (sniff) this packet andcan compute ranges using TDoA; (anchors have been previously maintainingtime synchronization using any of the techniques disclosed herein, orother such techniques as would be apparent to one of ordinary skill inthe art). FIG. 3B shows an archetypal ranging operation, where the nodeN440 sends communication to M410 (transaction 441), which is alsosniffed by sniffers 5420 (transaction 443) and S430 (transaction 442).

As disclosed in U.S. Pat. No. 10,757,675 and U.S. patent applicationSer. No. 16/283,465 and would be apparent to one of ordinary skill inthe art, wider bandwidth (>=80 Mhz) packets are preferred. However,narrower bandwidths can also be used, with less accuracy.

No direct interaction or protocols are needed between the tracker andanchors, assuming all are awake and tuned to the same channel; directinteraction can occur if desired. In one embodiment, an additional nodeN408 shown in FIG. 3C may be communicating with N440 directly, whileM410, 5420, and S430 may not have direct communication with N440 and mayonly be managing the overall set of operations and/or sniffing thetransactions.

FIGS. 5A-5C illustrate a method for performing a TDoA ranging forlocalization as discussed in conjunction with the description of FIGS.4A and 4B in accordance with one embodiment. The operations of thismethod may be executed by a wireless device, a wireless control deviceof a hub (e.g., an apparatus), a system, or a remote device, computer,or cloud service which includes processing circuitry or processinglogic. The processing logic may include hardware (circuitry, dedicatedlogic, etc.), software (such as is run on a general purpose computersystem or a dedicated machine or a device), or a combination of both. Inone embodiment, an anchor node, a hub, a wireless device, or a remotedevice, computer, or cloud service performs the operations of thismethod. Algorithms associated with the various computations may beperformed in a remote computer to which the relevant data associatedwith timing and distance measurements is sent. The remote device orcomputer may be at a different location (e.g., different network, in thecloud) than the wireless network architecture having a plurality ofwireless nodes. The remote device or computer may be at a differentlocation within the wireless network architecture than certain nodesthat are transmitted and receiving communications within the wirelessnetwork architecture. Any of the parameters (e.g., time stamps, receiverdelays, transceiver delays, CSI, etc.) determined for a first wirelessnode or a second wireless node of an operation can also be determinedfor both of the first and second wireless nodes or any of the wirelessnodes of the wireless network architecture.

At operation 502, the method includes initializing a wireless networkarchitecture having first and second wireless anchor nodes and aplurality of wireless sensor nodes. At operation 504, processing logicof one of the wireless nodes having a wireless control device causes awireless network of nodes to be configured as a mesh-based networkarchitecture for a time period (e.g., predetermined time period, timeperiod sufficient for localization, etc.) for localization of a trackerdevice (e.g., wireless node, tracker) having an unknown location. In oneexample, the wireless network is configured as a tree-like low powernetwork in combination with a temporary mesh-based network.

At operation 506, the method includes creating multiple distancecandidates between a tracker device having an unknown location and afirst wireless node by using a known signal travel time between thefirst wireless node and a second wireless node. At operation 508, themethod includes obtaining, with the first wireless node, a receive timestamp of reception of a transmission from the tracker device.

At operation 510, the method includes obtaining, with the secondwireless node, a receive time stamp of reception of the transmissionfrom the tracker device. At operation 511, the method includesobtaining, with the first wireless node, a receive time stamp ofreception of a transmission from the second wireless node. At operation512, the method includes obtaining, with the second wireless node, atransmit time stamp for a transmission from the second wireless node. Atoperation 514, the method includes generating a clock frequency offsetestimation from the first wireless node, obtaining a first channel stateinformation from the first wireless node receiving a transmission fromthe tracker device, obtaining a second channel state information fromthe first wireless node receiving a transmission from the secondwireless node, generating a combined channel state information from thefirst and second channel state information from reception of thetransmissions from the tracker device and the second wireless node andobtaining receiver state dependent delay of the first wireless node (orobtaining receiver state dependent delay of the first and secondwireless nodes). Carrier frequency offset estimation is an integral partof a digital receiver. Typically, carrier frequency offset is measuredfrom a dedicated training signal, like WiFi Short/Long Training Symbols.Since the carrier and symbol clock are typically derived from the samesource, then any measured carrier frequency offset can be assumed to befound in the clock used for the time stamps too. A clock frequencyoffset estimation between the first and second wireless nodes includes aclock and carrier frequency offset. Receivers typically have differentoperating states depending on e.g. on the incoming signal strength andgain settings. These states can introduce additional delay (e.g.,receiver state dependent delay of the first wireless node, receiverstate dependent delay of the second wireless node) that can be takeninto account when estimating the distances.

At operation 516, the combined channel state information is formed froma list of path distances from the second wireless node to the firstwireless node ordered from shortest to longest and containing only jelements near the strongest path element, and from a list of pathdistances from the tracker device to the first wireless node orderedfrom shortest to longest and containing only k elements near thestrongest path element.

At operation 518, a correct direct path from the second wireless node tothe first wireless node is estimated using the known signal travel timebetween the first and second wireless nodes, the receive time stamp ofthe first wireless node, a transmit time stamp for a transmission of thesecond wireless node, and a measured history of a clock offset betweenthe first and second wireless nodes.

At operation 520, j times k long list of combined channel stateinformation is formed by subtracting each of j distances from each of kdistances.

At operation 522, j times k times m differential distance estimatecandidates are formed by subtracting each combined channel statedistance from each of the m path distances from the tracker device tothe second wireless node where m paths are close to the strongest pathand ordered according to delay. In one example, some of the distanceestimate candidates are removed when the distance estimate candidatesare not between predetermined limits. The predetermined limits arecalculated from the known locations of the first and second wirelessnodes and from a shape of a space where the tracker device is known tobe.

At operation 524, combining differential distance estimates with receivetime stamp and transceiver delay of the second wireless node (ortransceiver delay of the first and second wireless nodes) is used forTDoA multilateration. In one example, j times k plus m paths togetherwith the times stamps are used in multilateration. The multilaterationfinds multiple possible locations and corresponding multiple clockoffsets between the tracker device and the first wireless node andwherein one location is selected that matches (e.g., best matches) aclock offset with a distance between the known location of the firstwireless node and a possible location of the tracker device. Thedistance estimate candidates in multilateration are weighted based onpreviously determined reliability metrics.

At operation 526, the combined channel state information is formed froma list of path distances from the second wireless node ordered fromshortest to longest and containing only elements near the strongest pathelement from the first wireless node, from list of path distances fromthe tracker device ordered from shortest to longest and containing onlyelements near the strongest path element from the second wireless node,and from list of possible distances between the second wireless node andthe tracker device.

At operation 528, n times m times j long extended distance candidatelist is formed by adding together each of the n path distances from thefirst wireless node, each of the m path distances from the secondwireless node and each distance in list of possible distances betweenthe second wireless node and the tracker device.

At operation 530, the method further includes combining the extendeddistance candidate list, receive time stamp for the second wirelessdevice, and transceiver delay for the second wireless device (ortransceiver delays of the first and second wireless nodes) fortrilateration.

At operation 532, the method further includes receiver and transceiverdelays for the second wireless node (or receiver and transceiver delaysof the first and second wireless nodes) that are taken from a tablecontaining delays previously measured for all transceiver states.

At operation 534, the method further includes reporting, with thetracker device, an identifier that can be used to find previouslymeasured transmitter or receiver frequency responses in a list. Atoperation 536, the identified transmitter or receiver frequency responseis used to adjust the channel state information of the first and secondwireless nodes.

At operation 538, the processing logic of the wireless node (e.g., hub,anchor node, wireless device, remote device or computer) configures thewireless network in a tree based or tree-like network architecture (ortree architecture with no mesh-based features) upon completion oflocalization of the tracking device. The temporary mesh-based featuresare terminated or disabled upon completion of localization.

Since the existence of the sniffers need not be known by the tracker orby devices it is communicating with, it is possible to implement TDoAusing devices not aware of TDoA. Aspects of the present invention may beutilized to track a device in a wireless local area network (WLAN)context. FIG. 6 illustrates a method for monitoring a tracker device ina WLAN (e.g., IEEE 802.11, WiFi) context in accordance with oneembodiment. The operations of this method may be executed by a wirelessdevice, a wireless control device of a hub (e.g., an apparatus), asystem, or a remote device, computer, or cloud service which includesprocessing circuitry or processing logic. The processing logic mayinclude hardware (circuitry, dedicated logic, etc.), software (such asis run on a general purpose computer system or a dedicated machine or adevice), or a combination of both. In one embodiment, an anchor node, ahub, a wireless device, or a remote device, computer, or cloud serviceperforms the operations of this method. Algorithms associated with thevarious computations may be performed in a remote computer to which therelevant data associated with timing and distance measurements is sent.The remote device or computer may be at a different location (e.g.,different network, in the cloud) than the wireless network architecturehaving a plurality of wireless nodes. The remote device or computer maybe at a different location within the wireless network architecture thancertain nodes that are transmitted and receiving communications withinthe wireless network architecture.

At operation 602, the method includes initializing a wireless networkarchitecture having first and second wireless anchor nodes and aplurality of wireless sensor nodes. In one example, the wireless networkis configured as a tree-like network.

At operation 603, a tracker device enters a wireless coverage area ofthe wireless network architecture and associates to a WLAN access point(AP), which can be one of the anchor nodes. At operation 604, the AP ortracker device notifies a ranging coordinator that a tracker device hasassociated, along with its operating channel. At operation 606,processing logic of one of the wireless nodes having a wireless controldevice causes a wireless network of nodes to be configured partially asa mesh-based network architecture for localization of the tracker device(e.g., wireless node, tracker) having an unknown location and partiallyas a tree-like network. In one example, the wireless network isconfigured as a tree-like network in combination with a mesh-basednetwork. The sniffing anchor nodes can be considered part of a meshnetwork and the AP and the tracker device being located can beconsidered part of a tree network. The mesh network is sniffingtransmissions from the tree network and the mesh network may beconfigured to continuously sniff/receive packets from the trackerdevice.

At operation 607, the ranging coordinator adds the tracker device to atracking schedule and distributes the schedule to various nodes. In oneexample, the ranging coordinator receives channel update informationfrom the wireless tracker arbitrary device and any other wirelessarbitrary devices and distributes a ranging schedule to the wirelessnodes (e.g., wireless tracker device and first and second wirelessanchor nodes). The first or second wireless anchor node will change tothe operating channel of the wireless tracker device when packets arebeing transmitted for ranging. At operation 608, the ranging coordinatorcan optionally request the AP to stimulate the tracker device totransmit; alternatively or additionally, the ranging coordinator candirectly request the tracker to transmit. The tracker device may alsouse an internal event (e.g., timer or sensor) to trigger transmision.

At operation 609, the method includes receiving, with the first andsecond wireless anchor nodes, packets from the tracker device. When thetracker device transmits any packet, the anchor nodes may sniff thepacket transmissions and measure, define or calculate their associatedtimestamps and CSI, and relay ranging data to a locationing processor.

At operation 610, the method performs time difference of arrival (TDoA)ranging of the reception of the packets between each of the first andthe second wireless anchor nodes. At operation 611, the locationingprocessor of a wireless node or a remote device calculates a locationresult for the tracker device.

At operation 612, software of the wireless tracker device or software ofone of the anchor nodes causes the wireless tracker device to transmitpackets more frequently when the tracker device is moving (in motion) toallow the TDoA ranging to determine location of the wireless trackerdevice.

At operation 613, the first or second wireless anchor node is configuredto determine a source address (e.g., MAC address) from packets of thewireless tracker device to identify the wireless tracker device evenwhen payload of the packets are encrypted.At operation 618, the wirelesstracker device may beconfigured to transmit during its assigned scheduleslot according to a ranging schedule received from the rangingcoordinator.

At operation 620, the processing logic of the wireless node (e.g., hub,anchor node, wireless device, remote device or computer) configures thewireless network at least partially in a tree based or tree-like networkarchitecture upon completion of localization. The mesh-based featurescan be continuous or temporary.

In one embodiment, the tracker device can be any arbitrary WLAN (e.g.,OFDM WiFi) device maintaining a WLAN (e.g.,WiFi) association to anarbitrary AP. The tracker will transmit packets to the AP when thetracker has data to send and additionally keep-alive packets to maintainits association. Any and all of these packets may be used for TDOAranging. Software on the tracker can be used to ensure that the trackertransmits frequently enough when in motion such that TDOA ranging cantrack movements. Alternatively or additionally, software protocols onthe AP (or other parts of the network) can stimulate the tracker totransmit more frequently or at a specific time. Current WiFi standardsrequire that the source MAC address of the tracker will be constant forat least the life of the association. The source address can be used todistinguish trackers and the payload of the tracker packets may beencrypted (since it has no impact to TDOA ranging).

In another embodiment, it is also possible to perform TDoA on arbitrarydevices that are not WLAN associated with the AP. The arbitrary devicesends probe request packets to discover networks that are available.TDoA can be done on these probe request packets sent by devices thataren't WLAN associated or may be associated to a different network.

TDoA requires all anchors participating in the ranging to be tuned tothe tracker's channel when the tracker transmits for ranging. LargerWiFi AP deployments typically utilize many channels, therefore anchorssplit time across multiple channels in order to monitor all trackers. ARanging Coordinator software function may be used to coordinateactivities of trackers and anchors. In one example, all devices need aglobal time reference, such as network time protocol (NTP). In such asystem, the Ranging Coordinator will: (1) receive channel updateinformation from trackers and (2) distribute a ranging schedule totrackers and anchors. The trackers will: (1) report any association orchannel changes to the coordinator and (2) receive schedule updates fromthe coordinator and ensure that the tracker transmits during itsassigned schedule slot. The anchors will receive schedule updates fromthe coordinator which specify the time, channel, and which trackers tosearch for/track.

Tracking of multiple nodes may be performed. In this case, variouspossible implementations are possible with a Ranging Coordinator. In oneembodiment, the packets from nodes with unknown locations to be trackedare captured serially. In another embodiment, these are captured inparallel, for example, by using different channels or by ensuringsufficient spatial separation between transmitting nodes such thatinterference is minimized. More generally, by using multiple channelsand exploiting the spatial separation and signal attenuation over thesedistances, it is possible to capture packets across multiple channelsand multiple sources and build a comprehensive location map of multipletrackers simultaneously.

Since the existence of the sniffers need not be known by the tracker orby devices it is communicating with, it is possible to implement TDoAusing devices not aware of TDoA and rather only aware of TOA-basedranging as is implemented in some existing and emerging WLAN (e.g., WiFistandards). One such embodiment is shown in FIG. 1 .

In such a system, anchor functionality may or may not be integrated withregular WiFi AP function into the same wireless node. Anchors advertisesupport for fine time measurement (FTM) protocol Responder (e.g., usingWiFi beacons and/or probe responses) as implemented in some existing andemerging WiFi standards such as 802.11mc and 802.11az. The FTM protocolprovides a way for two wireless local area network (WLAN) devices toperform round trip time (RTT) and estimate a distance between eachother. The FTM protocol is inclusive of all forms of WLAN RTT ranging(e.g., IEEE 802.11, 802.11mc, 802.11az, etc.). For implementation ofTDoA, nearby anchors will all be tuned to the same channelsimultaneously, either indefinitely or per a schedule. As described bythe aforementioned standards, FTM Initiator-capable trackers (e.g.,N440) scan for anchors (e.g., wireless nodes M410, 5420, S430) andperform TOA ranging to these anchor nodes serially. To implement, TDoA,nearby anchors (e.g., S420, S430) receive (sniff) the TOA ranginginteraction and data from all anchors is used to perform TDOAlocalization. A single TOA FTM ranging operation as embodied withinexisting and emerging WiFi standards can therefore produce a locationresult through TDoA, despite the fact that the devices being tracked maynot/need not be aware of the performance of this TDoA operation.

It is possible to use novel aspects of the present disclosure herein tolocate a tracker using arbitrary anchors. An example of such a wirelesssystem is shown in FIG. 7 .

To explain FIG. 7 , the following definitions are first provided: (1)CSI-enabled device: a device capable of sniffing and collecting CSI andtimestamps (shown as a triangle in FIG. 7 ). (2) Arbitrary device: anyWLAN (e.g., OFDM WiFi) device (shown as circle) (3) Anchor: a stationarydevice (with known coordinates).

Any pair of CSI-enabled devices (S420, S430) can measure a TDOA range toan arbitrary device (N440), which is transmitting to any destinationaddress (e.g., its associated AP); this range can be represented by ahyperbolic shape. In one example, the pair of CSI-enabled devices mustbe time synchronized. TOA reference ranging can accomplish this usingthe techniques discussed above or using the techniques described in U.S.Pat. No. 10,757,675 and U.S. patent application Ser. No. 16/283,465, orother such techniques as would be apparent to one of ordinary skill inthe art.

One of the CSI-enabled devices (S420) is an anchor. The otherCSI-enabled device (S430) is a tracker with unknown location. The pairof CSI-enabled devices can measure TDOA ranges to multiple (3 or 4)arbitrary anchors (one such anchor is show in FIG. 7 as N440) one at atime. The ranges can be used with various triangulation methods todetermine the location of the tracker, such as discussed in U.S. Pat.No. 10,757,675 and U.S. patent application Ser. No. 16/283,465 or othersuch techniques as would be apparent to one of ordinary skill in theart.

Arbitrary anchors transmit with sufficient frequency to enable thetracking operation. This can be achieved using the aforementionedscheduling techniques, or other such techniques as would be apparent toone of ordinary skill in the art. For example, 5420 can stimulateanchors to transmit if it is associated to the same network.

To determine the absolute or relative location of the object to betracked, it is necessary to know the location of the anchors, either interms of absolute physical location or in terms of relative locationwith respect to each other. In one embodiment, the user can place theanchors in exact known locations and make this information available tothe triangulation algorithms.

In another embodiment, anchor free localization (e.g., brute forcesearch, exhaustive search, triangulation, numerical optimizers,probabilistic methods, linear algebra solution, incremental methods,etc.) can be used, such as described in U.S. patent application Ser. No.16/283,478 or other such techniques as would be apparent to one ofordinary skill in the art. FIG. 8 illustrates an anchor free method forlocalization of wireless devices of a wireless sensor network inaccordance with one embodiment. The operations of this method may beexecuted by a wireless device, a wireless control device of a hub (e.g.,an apparatus), a system, or a remote device, computer, or cloud servicewhich includes processing circuitry or processing logic. The processinglogic may include hardware (circuitry, dedicated logic, etc.), software(such as is run on a general purpose computer system or a dedicatedmachine or a device), or a combination of both. In one embodiment, ananchor node, a hub, a wireless device, or a remote device, computer, orcloud service performs the operations of this method. Algorithmsassociated with the various computations may be performed in a remotecomputer to which the relevant data associated with timing and distancemeasurements is sent. The remote device or computer may be at adifferent location (e.g., different network, in the cloud) than thewireless network architecture having a plurality of wireless nodes. Theremote device or computer may be at a different location within thewireless network architecture than certain nodes that are transmittedand receiving communications within the wireless network architecture.

At operation 802, arbitrary anchor devices can be arbitrarily placed atunknown, fixed locations typically within a building. The user has theoption to roughly place the arbitrary anchors on a map to aid inconvergence. At operation 804, the user can place the tracker having anunknown location near each arbitrary anchor one at a time. At operation806, the tracker ranges to all arbitrary anchors, thus building a matrixof ranges in which the Anchor Free methods at operation 808 can used toderive relative positions of all anchor devices. Device to deviceranging data is used to associate an arbitrary anchor device with arelative location. Relative locations of all anchor nodes or at least asubset of anchor nodes are determined using at least one of optimizationtechniques, brute force methods, probabilistic methods, etc. Multiplepath estimates for each range can be fed into the anchor free algorithmfor calculating the relative locations.

At operation 810, the anchor free method will then match/snap the roughplacement if available and relative positions to the map, and/or theuser rotates and scales the relative positions to fit the map. Therotation, translation, and mirroring of a full set of relative positionsare adjusted to align them to a physical description of the space orenvironment (e.g., floorplan, map, etc). Machine learning, artificialintelligence, or a user may perform these adjustments. In one example,machine learning generates a likely set of orientations for relativepositions with respect to the space or environment and then a userselects one of the orientations. These adjustments place the anchorpositions in the coordinate system of the space or environment. Atoperation 812, these anchor nodes and their calculated positions withinthe space or environment are determined.

Once these anchor locations have been determined, at operation 814 theseanchor nodes and associated anchor locations are utilized for rangingmeasurements between the anchor nodes and any nodes (e.g., mobiletrackers) having an unknown location (e.g., fixed or moving locations).These anchor nodes can be used for ToA or TDoA ranging measurements. Atoperation 816, numerous methods including at least one of brute forcecalculation, triangulation, and numerical optimizers can be used todetermine the unknown locations for nodes (e.g., trackers, wirelessnodes, wireless sensor nodes) that correspond to the measured rangingdata. At operation 818, the processing logic of the wireless node (e.g.,hub, anchor node, wireless device, remote device or computer) configuresthe wireless network in a tree based or tree-like network architecture(or tree architecture with no mesh-based features) upon completion oflocalization. Processing logic of the wireless node having a wirelesscontrol device causes a wireless network of nodes to be configured as amesh-based network architecture for a time period (e.g., predeterminedtime period, time period sufficient for localization, etc.) forlocalization of at least one wireless device (e.g., wireless node,tracker) having an unknown location. In one example, the wirelessnetwork is configured as a tree-like low power network in combinationwith a temporary mesh-based network.

Although the operations in the computer-implemented methods of FIGS.5A-5C, 6A-6B, and 8 are shown in a particular order, the order of theactions can be modified. Thus, the illustrated embodiments can beperformed in a different order, and some operations may be performed inparallel. Some of the operations listed in FIGS. 5A-5C, 6A-6B, and 8 maybe optional in accordance with certain embodiments. The numbering of theoperations presented is for the sake of clarity and is not intended toprescribe an order of operations in which the various operations mustoccur. Additionally, operations from the various flow diagrams may beutilized in a variety of combinations.

In another embodiment, fingerprint-based set-up and localization may beused. During setup of the system, the user places the tracker nearvarious locations of interest in the home (e.g., the center of eachroom) one at a time. The tracker ranges to all arbitrary anchors and thesystem records these ranges along with the name of the location ofinterest. During normal operation: the location algorithm searches for amatch between the current location and a location of interest and thelocation result is presented as proximity (or not) to a location ofinterest (rather than coordinates on a map).

In one embodiment, the baseband hardware of a transceiver of a wirelessnode allows full duplex operation. In this case, the signal can betransmitted and then immediately received after going through thetransmit and receive chains. The CSI, transmit, and receive timestampsare combined to generate a calibration profile for the hardware of anywireless node. The delay can be extracted and removed directly or thefrequency response of the hardware itself can be removed from subsequentmeasurements.

In another embodiment, the baseband hardware of a transceiver of awireless node is not full duplex. In this case the transmit packet canbe generated independently from the baseband. The raw data for a packetcan be stored in memory and read out directly to a digital-to-analogconverter (DAC). It goes through the transmit (TX) and receive (RX) RFchains as before. The baseband is set to be in receive mode and cancapture the CSI and timestamp of the incoming packet. The CSI, transmit,and receive timestamps can be used as in the previous case. The transmittimestamp needs to be captured at the time the memory readout to the DACis triggered.

The implementation of the radio-frequency communication between theterminal nodes and the hubs may be implemented in a variety of waysincluding narrow-band, channel overlapping, channel stepping,multi-channel wide band, and ultra-wide band communications.

The hubs may be physically implemented in numerous ways in accordancewith embodiments of the invention. FIG. 9A shows an exemplary embodimentof a hub implemented as an overlay 1500 for an electrical power outletin accordance with one embodiment. The overlay 1500 (e.g., faceplate)includes a hub 1510 and a connection 1512 (e.g., communication link,signal line, electrical connection, etc.) that couples the hub to theelectrical outlet 1502. Alternatively (or additionally), the hub iscoupled to outlet 1504. The overlay 1500 covers or encloses theelectrical outlets 1502 and 1504 for safety and aesthetic purposes.

FIG. 9B shows an exemplary embodiment of an exploded view of a blockdiagram of a hub 1520 implemented as an overlay for an electrical poweroutlet in accordance with one embodiment. The hub 1520 includes a powersupply rectifier 1530 that converts alternating current (AC), whichperiodically reverses direction, to direct current (DC) which flows inonly one direction. The power supply rectifier 1530 receives AC from theoutlet 1502 via connection 1512 (e.g., communication link, signal line,electrical connection, etc.) and converts the AC into DC for supplyingpower to a controller circuit 1540 via a connection 1532 (e.g.,communication link, signal line, electrical connection, etc.) and forsupplying power to RF circuitry 1550 via a connection 1534 (e.g.,communication link, signal line, electrical connection, etc.). Thecontroller circuit 1540 includes memory 1542 or is coupled to memorythat stores instructions which are executed by processing logic 1544(e.g., one or more processing units) of the controller circuit 1540 forcontrolling operations of the hub for forming, monitoring, andperforming localization of the wireless asymmetrical network asdiscussed herein. The RF circuitry 1550 may include a transceiver orseparate transmitter 1554 and receiver 1556 functionality for sendingand receiving bi-directional communications via antenna(s) 1552 with thewireless sensor nodes. The RF circuitry 1550 communicatesbi-directionally with the controller circuit 1540 via a connection 1534(e.g., communication link, signal line, electrical connection, etc.).The hub 1520 can be a wireless control device 1520 or the controllercircuit 1540, RF circuitry 1550, and antenna(s) 1552 in combination mayform the wireless control device as discussed herein.

FIG. 10A shows an exemplary embodiment of a hub implemented as a cardfor deployment in a computer system, appliance, or communication hub inaccordance with one embodiment. The card 1662 can be inserted into thesystem 1660 (e.g., computer system, appliance, or communication hub) asindicated by arrow 1661.

FIG. 10B shows an exemplary embodiment of a block diagram of a hub 1664implemented as a card for deployment in a computer system, appliance, orcommunication hub in accordance with one embodiment. The hub 1664includes a power supply 1666 that provides power (e.g., DC power supply)to a controller circuit 1668 via a connection 1674 (e.g., communicationlink, signal line, electrical connection, etc.) and provides power to RFcircuitry 1670 via a connection 1676 (e.g., communication link, signalline, electrical connection, etc.). The controller circuit 1668 includesmemory 1661 or is coupled to memory that stores instructions which areexecuted by processing logic 1663 (e.g., one or more processing units)of the controller circuit 1668 for controlling operations of the hub forforming, monitoring, and performing localization of the wirelessasymmetrical network as discussed herein. The RF circuitry 1670 mayinclude a transceiver or separate transmitter 1675 and receiver 1677functionality for sending and receiving bi-directional communicationsvia antenna(s) 1678 with the wireless sensor nodes. The RF circuitry1670 communicates bi-directionally with the controller circuit 1668 viaa connection 1672 (e.g., communication link, signal line, electricalconnection, etc.). The hub 1664 can be a wireless control device 1664 orthe controller circuit 1668, RF circuitry 1670, and antenna(s) 1678 incombination may form the wireless control device as discussed herein.

FIG. 10C shows an exemplary embodiment of a hub implemented within anappliance (e.g., smart washing machine, smart refrigerator, smartthermostat, other smart appliances, etc.) in accordance with oneembodiment. The appliance 1680 (e.g., smart washing machine) includes ahub 1682.

FIG. 10D shows an exemplary embodiment of an exploded view of a blockdiagram of a hub 1684 implemented within an appliance (e.g., smartwashing machine, smart refrigerator, smart thermostat, other smartappliances, etc.) in accordance with one embodiment. The hub includes apower supply 1686 that provides power (e.g., DC power supply) to acontroller circuit 1690 via a connection 1696 (e.g., communication link,signal line, electrical connection, etc.) and provides power to RFcircuitry 1692 via a connection 1698 (e.g., communication link, signalline, electrical connection, etc.). The controller circuit 1690 includesmemory 1691 or is coupled to memory that stores instructions which areexecuted by processing logic 1688 (e.g., one or more processing units)of the controller circuit 1690 for controlling operations of the hub forforming, monitoring, and performing localization of the wirelessasymmetrical network as discussed herein. The RF circuitry 1692 mayinclude a transceiver or separate transmitter 1694 and receiver 1695functionality for sending and receiving bi-directional communicationsvia antenna(s) 1699 with the wireless sensor nodes. The RF circuitry1692 communicates bi-directionally with the controller circuit 1690 viaa connection 1689 (e.g., communication link, signal line, electricalconnection, etc.). The hub 1684 can be a wireless control device 1684 orthe controller circuit 1690, RF circuitry 1692, and antenna(s) 1699 incombination may form the wireless control device as discussed herein.

In one embodiment, an apparatus (e.g., hub) for providing a wirelessasymmetric network architecture includes a memory for storinginstructions, processing logic (e.g., one or more processing units,processing logic 1544, processing logic 1663, processing logic 1688,processing logic 1763, processing logic 1888) of the hub to executeinstructions to establish and control communications in a wirelessasymmetric network architecture, and radio frequency (RF) circuitry(e.g., RF circuitry 1550, RF circuitry 1670, RF circuity 1692, RFcircuitry 1890) including multiple antennas (e.g., antenna(s) 1552,antenna(s) 1678, antenna(s) 1699, antennas 1311, 1312, and 1313, etc.)to transmit and receive communications in the wireless asymmetricnetwork architecture. The RF circuitry and multiple antennas to transmitcommunications to a plurality of sensor nodes (e.g., node 1, node 2)each having a wireless device with a transmitter and a receiver (ortransmitter and receiver functionality of a transceiver) to enablebi-directional communications with the RF circuitry of the apparatus inthe wireless asymmetric network architecture.

In one example, a first wireless node includes a wireless device withone or more processing units and RF circuitry for transmitting andreceiving communications in the wireless network architecture includinga first RF signal having a first packet. A second wireless node includesa wireless device with a transmitter and a receiver to enablebi-directional communications with the first wireless node in thewireless network architecture including a second RF signal with a secondpacket. The one or more processing units of the first wireless node areconfigured to execute instructions to determine a round trip timeestimate of the first and second packets, to determine channel stateinformation (CSI) of the first and second wireless nodes, and tocalibrate hardware to determine hardware delays of the first and secondwireless nodes.

In one example, the apparatus is powered by a mains electrical sourceand the plurality of sensor nodes are each powered by a battery sourceto form the wireless network architecture.

Various batteries could be used in the wireless sensor nodes, includinglithium-based chemistries such as Lithium Ion, Lithium Polymer, LithiumPhosphate, and other such chemistries as would be apparent to one ofordinary skill in the art. Additional chemistries that could be usedinclude Nickel metal hydride, standard alkaline battery chemistries,Silver Zinc and Zinc Air battery chemistries, standard Carbon Zincbattery chemistries, lead Acid battery chemistries, or any otherchemistry as would be obvious to one of ordinary skill in the art.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the required method operations.

FIG. 11 illustrates a block diagram of a sensor node in accordance withone embodiment. The sensor node 1700 includes a power source 1710 (e.g.,energy source, battery source, primary cell, rechargeable cell, etc.)that provides power (e.g., DC power supply) to a controller circuit 1720via a connection 1774 (e.g., communication link, signal line, electricalconnection, etc.), provides power to RF circuitry 1770 via a connection1776 (e.g., communication link, signal line, electrical connection,etc.), and provides power to sensing circuitry 1740 via a connection1711 (e.g., communication link, signal line, electrical connection,etc.). The controller circuit 1720 includes memory 1761 or is coupled tomemory that stores instructions which are executed by processing logic1763 (e.g., one or more processing units) of the controller circuit 1720for controlling operations of the sensor node for forming and monitoringthe wireless asymmetrical network as discussed herein. The RF circuitry1770 (e.g., communication circuitry) may include a transceiver orseparate transmitter 1775 and receiver 1777 functionality for sendingand receiving bi-directional communications via antenna(s) 1778 with thehub(s) and optional wireless sensor nodes. The RF circuitry 1770communicates bi-directionally with the controller circuit 1720 via aconnection 1772 (e.g., electrical connection). The sensing circuitry1740 includes various types of sensing circuitry and sensor(s) includingimage sensor(s) and circuitry 1742, moisture sensor(s) and circuitry1743, temperature sensor(s) and circuitry, humidity sensor(s) andcircuitry, air quality sensor(s) and circuitry, light sensor(s) andcircuitry, motion sensor(s) and circuitry 1744, audio sensor(s) andcircuitry 1745, magnetic sensor(s) and circuitry 1746, and sensor(s) andcircuitry n, etc.

The wireless localization techniques disclosed herein may be combinedwith other sensed information to improve localization accuracy of theoverall network. For example, in wireless sensors in which one or moreof the nodes contain cameras, captured images can be used with imageprocessing and machine learning techniques to determine whether thesensor nodes that are being monitored are looking at the same scene andare therefore likely in the same room. Similar benefits can be achievedby using periodic illumination and photodetectors. By strobing theillumination and detecting using the photodetectors, the presence of anoptical path can be detected, likely indicating the absence of opaquewalls between the strobe and the detector. In other embodiments,magnetic sensors can be integrated into the sensor nodes and used as acompass to detect the orientation of the sensor node that is beingmonitored. This information can then be used along with localizationinformation to determine whether the sensor is on the wall, floor,ceiling, or other location.

In one example, each sensor node may include an image sensor and eachperimeter wall of a house includes one or more sensor nodes. A hubanalyzes sensor data including image data and optionally orientationdata along with localization information to determine absolute locationsfor each sensor node. The hub can then build a three dimensional imageof each room of a building for a user. A floor plan can be generatedwith locations for walls, windows, doors, etc. Image sensors may captureimages indicating a change in reflections that can indicate homeintegrity issues (e.g., water, leaking roof, etc.).

FIG. 12 illustrates a block diagram of a system 1800 having a hub inaccordance with one embodiment. The system 1800 includes or isintegrated with a hub 1882 or central hub of a wireless asymmetricnetwork architecture. The system 1800 (e.g., computing device, smart TV,smart appliance, communication system, etc.) may communicate with anytype of wireless device (e.g., cellular phone, wireless phone, tablet,computing device, smart TV, smart appliance, etc.) for sending andreceiving wireless communications. The system 1800 includes a processingsystem 1810 that includes a controller 1820 and processing units 1814.The processing system 1810 communicates with the hub 1882, anInput/Output (I/0) unit 1830, radio frequency (RF) circuitry 1870, audiocircuitry 1860, an optics device 1880 for capturing one or more imagesor video, an optional motion unit 1844 (e.g., an accelerometer,gyroscope, etc.) for determining motion data (e.g., in three dimensions)for the system 1800, a power management system 1840, andmachine-accessible non-transitory medium 1850 via one or morebi-directional communication links or signal lines 1898, 1818, 1815,1816, 1817, 1813, 1819, 1811, respectively.

The hub 1882 includes a power supply 1891 that provides power (e.g., DCpower supply) to a controller circuit 1884 via a connection 1885 (e.g.,communication link, signal line, electrical connection, etc.) andprovides power to RF circuitry 1890 via a connection 1887 (e.g.,communication link, signal line, electrical connection, etc.). Thecontroller circuit 1884 includes memory 1886 or is coupled to memorythat stores instructions which are executed by processing logic 1888(e.g., one or more processing units) of the controller circuit 1884 forcontrolling operations of the hub for forming and monitoring thewireless asymmetrical network as discussed herein. The RF circuitry 1890may include a transceiver or separate transmitter (TX) 1892 and receiver(RX) 1894 functionality for sending and receiving bi-directionalcommunications via antenna(s) 1896 with the wireless sensor nodes orother hubs. The RF circuitry 1890 communicates bi-directionally with thecontroller circuit 1884 via a connection 1889 (e.g., communication link,signal line, electrical connection, etc.). The hub 1882 can be awireless control device 1884 or the controller circuit 1884, RFcircuitry 1890, and antenna(s) 1896 in combination may form the wirelesscontrol device as discussed herein.

RF circuitry 1870 and antenna(s) 1871 of the system or RF circuitry 1890and antenna(s) 1896 of the hub 1882 are used to send and receiveinformation over a wireless link or network to one or more otherwireless devices of the hubs or sensors nodes discussed herein. Audiocircuitry 1860 is coupled to audio speaker 1862 and microphone 1064 andincludes known circuitry for processing voice signals. One or moreprocessing units 1814 communicate with one or more machine-accessiblenon-transitory mediums 1850 (e.g., computer-readable medium) viacontroller 1820. Medium 1850 can be any device or medium (e.g., storagedevice, storage medium) that can store code and/or data for use by oneor more processing units 1814. Medium 1850 can include a memoryhierarchy, including but not limited to cache, main memory and secondarymemory.

The medium 1850 or memory 1886 stores one or more sets of instructions(or software) embodying any one or more of the methodologies orfunctions described herein. The software may include an operating system1852, network services software 1856 for establishing, monitoring, andcontrolling wireless asymmetric network architectures, communicationsmodule 1854, and applications 1858 (e.g., home or building securityapplications, home or building integrity applications, developerapplications, etc.). The software may also reside, completely or atleast partially, within the medium 1850, memory 1886, processing logic1888, or within the processing units 1814 during execution thereof bythe device 1800. The components shown in FIG. 12 may be implemented inhardware, software, firmware or any combination thereof, including oneor more signal processing and/or application specific integratedcircuits.

Communication module 1854 enables communication with other devices. TheI/O unit 1830 communicates with different types of input/output (I/O)devices 1834 (e.g., a display, a liquid crystal display (LCD), a plasmadisplay, a cathode ray tube (CRT), touch display device, or touch screenfor receiving user input and displaying output, an optional alphanumericinput device).

Any of the following examples can be combined into a single embodimentor these examples can be separate embodiments. In one example of a firstembodiment, an asynchronous system for localization of nodes in awireless network architecture (e.g., wireless local area network (LAN),wireless wide area network (WAN), wireless cellular network) comprises afirst and second wireless nodes with at least one wireless node eachhaving a known locations and including a wireless device with one ormore processing units and RF circuitry for transmitting and receivingcommunications in the wireless network architecture; and a thirdwireless node having an unknown location and including a wireless devicewith RF circuitry to enable communications with the first and the secondwireless nodes in the wireless network architecture. The one or moreprocessing units of the first wireless node are configured to executeinstructions to receive a first communication from the third wirelessnode, to determine time difference of arrival (TDoA) information of thereception of the first communication between each of the first and thesecond wireless nodes, to determine TDoA ranging including a relative orabsolute position of the third wireless node using the time differenceof arrival information, to send a second communication with asynchronization packet received by the second wireless node, and tosynchronize the first and second wireless nodes based on the secondcommunication with the synchronization of the first and second wirelessnodes being decoupled from the first communication.

In another example of the first embodiment, the one or more processingunits of the first wireless node are configured to execute instructionsto determine transmission and reception timestamps of the secondcommunication, to determine channel state information of thesynchronization packet to calculate a distance between the first andsecond wireless nodes from known locations of the first and secondwireless nodes, wherein the synchronization of the first and secondwireless nodes further comprises determining a clock drift of the firstwireless node or the second wireless node.

In another example of the first embodiment, the synchronization of thefirst and second wireless nodes occurs less frequently than determininga relative or absolute position of the third wireless node.

In another example of the first embodiment, the synchronization of thefirst and second wireless nodes comprises calculation methods todetermine absolute clock phase difference at time of synchronization anda rate of change of the absolute clock phase difference.

In another example of the first embodiment, the first wireless node hasa first reference clock signal and the second wireless node has a secondreference clock signal.

In another example of the first embodiment, the synchronization isperformed on demand.

In another example of the first embodiment, the asynchronous wirelesssystem further comprises a fourth wireless node to send an initialcommunication to the third wireless node.

In another example of the first embodiment, the third wireless nodesends an initial communication to a fourth wireless node.

In another example of the first embodiment, a role of one of the first,second, or fourth wireless nodes is randomly or rotatably selected.

In another example of the first embodiment, a role of one of the first,second, or fourth wireless nodes is selected based on quality ofwireless communications to other wireless nodes or location within thewireless network architecture.

In another example of the first embodiment, TDoA ranging activity isused to cause synchronization when synchronization is needed.

In another example of the first embodiment, the asynchronous wirelesssystem further comprises a fifth wireless node having an unknownlocation and including a wireless device with RF circuitry to enablecommunications with other wireless nodes in the wireless networkarchitecture, wherein the one or more processing units of the firstwireless node are configured to execute instructions to receive a thirdcommunication from the fifth wireless node, to determine time differenceof arrival information of the reception of the fifth communicationbetween each of the first and the second wireless nodes, to determineranging including a relative or absolute position of the fifth wirelessnode using the time difference of arrival information

In another example of the first embodiment, packets from the third andfifth wireless nodes are captured serially.

In another example of the first embodiment, the asynchronous wirelesssystem, further comprises a fifth wireless node having an unknownlocation and including a wireless device with RF circuitry to enablecommunications with other wireless nodes in the wireless networkarchitecture. Packets from the third and fifth wireless nodes arecaptured in parallel by using a first RF channel to capture packets fromthe third wireless node and a second different RF channel to capturepackets from the fifth wireless node.

In another example of the first embodiment, the packets captured acrossthe first and second RF channels are used to build a comprehensivelocation map of the third and fifth wireless nodes simultaneously.

In another example of the first embodiment, packets from the third andfifth wireless nodes are captured in series during a first time periodand in parallel during a second time period depending on networkconditions within the wireless network architecture.

In another example of the first embodiment, one of the first and secondwireless nodes is a third party device.

In another example of the first embodiment, the first wireless nodesends addressed synchronization packets to anchor nodes individually orsends the synchronization packets with no addressing to all anchornodes.

In another example of the first embodiment, the first wireless nodesends a packet to the third wireless node and this packet is received bythe second wireless node and used for synchronization.

In another example of the first embodiment, this packet in combinationwith the second wireless node receiving packets between the firstwireless node and the third wireless node provides contention freetransmission and no overhead due to synchronization being performed withan acknowledgement packet.

In another example of the first embodiment, the first wireless node andthe third wireless node are configured to support fine time measurement(FTM) protocol and FTM packets.

In one example of a second embodiment, a computer implemented method forlocalization of nodes in a wireless network architecture (e.g., wirelesslocal area network (LAN), wireless wide area network (WAN), wirelesscellular network) comprises initializing the wireless networkarchitecture having first and second wireless nodes with at least onewireless node each having a known location. Each wireless node includesa wireless device with one or more processing units and RF circuitry fortransmitting and receiving communications in the wireless networkarchitecture. The method further includes receiving a firstcommunication from a third wireless node having an unknown location,determining time difference of arrival (TDoA) information upon receptionof the first communication between each of the first and the secondwireless nodes, determining TDoA ranging including a relative orabsolute position of the third wireless node using the time differenceof arrival information, sending a second communication with asynchronization packet that is received by the second wireless node, andsynchronizing the first and second wireless nodes based on the secondcommunication with the synchronization of the first and second wirelessnodes being decoupled from the first communication.

In another example of the second embodiment, the method further includesdetermining transmission and reception timestamps of the secondcommunication, determining channel state information of thesynchronization packet to calculate a distance between the first andsecond wireless nodes from known locations of the first and secondwireless nodes. The synchronization of the first and second wirelessnodes further comprises determining a clock drift of the first wirelessnode or the second wireless node.

In one example of a third embodiment, a computer implemented method forlocalization of a wireless arbitrary device in a wireless networkarchitecture, comprises initializing the wireless network architecturehaving first and second wireless anchor nodes and a plurality ofwireless sensor nodes, preparing, with the plurality of wireless anchornodes, for localization of the wireless arbitrary device that performswireless local area network (WLAN) active scanning or maintains a WLANassociation to any node. The method further includes receiving, with thefirst and second wireless anchor nodes, packets from the wirelessarbitrary device and performing time difference of arrival (TDoA)ranging upon reception of the packets between each of the first and thesecond wireless anchor nodes.

In another example of the third embodiment, software of the wirelessarbitrary device or software of its associated WLAN access point (AP) orsoftware of the first wireless anchor node to cause the wirelessarbitrary device to transmit packets more frequently when in motion toallow the TDoA ranging to determine location of the wireless arbitrarydevice.

In another example of the third embodiment, the wireless anchor nodesare configured to determine a source address from packets of thewireless arbitrary device to identify the wireless arbitrary device evenwhen payload of the packets are encrypted.

In another example of the third embodiment, the first or second wirelessanchor nodes comprise a ranging coordinator to tune the first and secondwireless anchor nodes to a RF channel of the wireless arbitrary devicewhen packets are being transmitted for ranging.

In another example of the third embodiment, the ranging coordinator toreceive channel update information from the wireless arbitrary deviceand any other wireless arbitrary devices and to distribute a rangingschedule to the wireless arbitrary devices and first and second wirelessanchor nodes.

In another example of the third embodiment, the wireless arbitrarydevice or its associated WLAN AP is configured to report any networkassociation or channel changes to the range coordinator, to receiveschedule updates from the range coordinator and ensure that the wirelessarbitrary device transmits during its assigned schedule slot.

In one example of a fourth embodiment, a computer implemented method foranchor free localization of wireless nodes in a wireless networkarchitecture, comprises arbitrarily positioning arbitrary anchor devicesat unknown, fixed locations, positioning a mobile tracker having anunknown location near each arbitrary anchor device one at a time,ranging the mobile tracker to the arbitrary anchor devices to build amatrix of ranges between the mobile tracker and the arbitrary anchordevices, and utilizing an Anchor Free algorithm and the matrix of rangesto derive relative positions of the arbitrary anchor devices.

In another example of the fourth embodiment, the matrix of rangesincludes device to device ranging data to associate an arbitrary anchordevice with a relative position.

In another example of the fourth embodiment, the computer implementedmethod further comprises matching or snapping relative locations of thearbitrary anchor devices to a map, determining positions of thearbitrary anchor devices, performing ranging measurements between thearbitrary anchor devices and the mobile tracker having an unknownlocation, and determining location of the mobile tracker using rangingdata from the ranging measurements.

In another example of the fourth embodiment, positioning a mobiletracker having an unknown location near each arbitrary anchor device oneat a time further comprises placing the mobile tracker near variouslocations of interest in a building one at a time.

In another example of the fourth embodiment, the computer implementedmethod further comprises recording ranges between the arbitrary anchordevices and the mobile tracker along with a name of the location ofinterest, during normal operation, searching for a match between acurrent location and a location of interest, and presenting a locationresult as proximity or not to a location of interest.

In one example of a fifth embodiment, a computer implemented method fora time difference of arrival (TDoA) ranging of wireless nodes in awireless network architecture, comprises creating multiple distanceestimate candidates between a tracker device have an unknown locationand a first wireless node by using a known signal travel time betweenthe first wireless node and a second wireless node, obtaining, with thefirst wireless node, a receive time stamp of reception of a transmissionfrom the tracker device, obtaining, with the second wireless node, areceive time stamp of reception of the transmission from the trackerdevice, obtaining, with the first wireless node, a receive time stamp ofreception of a transmission from the second wireless node, obtaining,with the second wireless node, a transmit time stamp for a transmissionfrom the second wireless node and generating a clock frequency offsetestimation from the first wireless node and a receiver state dependentdelay of the first wireless node.

In another example of the fifth embodiment, the computer implementedmethod further comprises obtaining first channel state information ofthe first wireless node upon reception of the transmission from thetracker device, obtaining second channel state information of the firstwireless node upon reception of the transmission from the secondwireless node, and generating a combined channel state information basedon the first and second channel state information from the reception ofthe transmissions from the tracker device and the second wireless node.

In another example of the fifth embodiment, the combined channel stateinformation is formed from a list of path distances from the secondwireless node to the first wireless node ordered from shortest tolongest and containing only j elements near a strongest path element,and from a list of path distances from the tracker device to the firstwireless node ordered from shortest to longest and containing only kelements near the strongest path element.

In another example of the fifth embodiment, a correct direct path fromthe second wireless node to the first wireless node is estimated usingthe known signal travel time between the first and second wirelessnodes, the receive time stamp of the first wireless node, a transmittime stamp for a transmission of the second wireless node, and ameasured history of a clock offset between the first and second wirelessnodes.

In another example of the fifth embodiment, j times k long list ofcombined channel state information is formed by subtracting each of jdistances from each of k distances.

In another example of the fifth embodiment, j times k times mdifferential distance estimate candidates are formed by subtracting eachcombined channel state distance from each of m path distances from thetracker device to the second wireless node where m paths are close tothe strongest path element and ordered according to delay.

In another example of the fifth embodiment, some of the distanceestimate candidates are removed when the distance estimate candidatesare not between predetermined limits.

In another example of the fifth embodiment, predetermined limits arecalculated from known locations of the first and second wireless nodesand from a shape of a space where the tracker device is known to be.

In another example of the fifth embodiment, combining differentialdistance estimates with receive time stamp and transceiver delay of thesecond wireless node is used for TDoA multilateration.

In another example of the fifth embodiment, where j times k plus m pathstogether with the time stamps are used in multilateration.

In another example of the fifth embodiment, the multilateration findsmultiple possible locations and corresponding multiple clock offsetsbetween the tracker device and the first wireless node and wherein onelocation is selected that matches a clock offset with a distance betweenthe known location of the first wireless node and a possible location ofthe tracker device.

In another example of the fifth embodiment, the distance estimatecandidates in multilateration are weighted based on previouslydetermined reliability metrics.

In another example of the fifth embodiment, the combined channel stateinformation is formed from a list of path distances from the secondwireless node ordered from shortest to longest and containing onlyelements near a strongest path element from the first wireless node,from list of path distances from the tracker device ordered fromshortest to longest and containing only elements near the strongest pathelement from the second wireless node, and from list of possibledistances between the second wireless node and the tracker device.

In another example of the fifth embodiment, n times m times j longextended distance candidate list is formed by combining each of n pathdistances from the first wireless node, each of the m path distancesfrom the second wireless node and each distance in list of possibledistances between the second wireless node and the tracker device.

In another example of the fifth embodiment, the computer implementedmethod further comprises combining the extended distance candidate list,receive time stamp for the second wireless device, and transceiver delayfor the second wireless device for trilateration.

In another example of the fifth embodiment, receiver and transceiverdelays for the second wireless node are taken from a table containingdelays previously measured for all transceiver states.

In another example of the fifth embodiment, the computer implementedmethod, further comprises reporting, with the tracker device, anidentifier that can be used to find previously measured transmitter orreceiver frequency responses in a list.

In another example of the fifth embodiment, the identified transmitteror receiver frequency response is used to adjust channel stateinformation of the first and second wireless nodes.

The phrase “at least one of A and B” should be understood to mean “onlyA, only B, or both A and B.” The phrase “at least one selected from thegroup of A and B” should be understood to mean “only A, only B, or bothA and B.” The phrase “at least one of A, B, or C” should be understoodto mean “only A, only B, only C, or any combination of A, B, or C.”

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention.The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

What is claimed is:
 1. An asynchronous wireless system for localizationof nodes in a wireless network architecture, comprising: first andsecond wireless nodes with at least one wireless node having a knownlocation and including a wireless device with one or more processingunits and RF circuitry for transmitting and receiving communications inthe wireless network architecture; and a third wireless node having anunknown location and including a wireless device with RF circuitry toenable communications with the first and the second wireless nodes inthe wireless network architecture, wherein the one or more processingunits of the first wireless node are configured to execute instructionsto receive a first communication from the third wireless node, todetermine time difference of arrival (TDoA) information of uponreception of the first communication between each of the first and thesecond wireless nodes, to determine TDoA ranging including a relative orabsolute position of the third wireless node using the time differenceof arrival information, to send a second communication with asynchronization packet received by the second wireless node, and tosynchronize the first and second wireless nodes based on the secondcommunication with the synchronization of the first and second wirelessnodes being independent and decoupled from the first communication. 2.The asynchronous wireless system of claim 1, wherein the one or moreprocessing units of the first wireless node are configured to executeinstructions to determine transmission and reception timestamps of thesecond communication, to determine channel state information of thesynchronization packet to calculate a distance between the first andsecond wireless nodes from known locations of the first and secondwireless nodes, wherein the synchronization of the first and secondwireless nodes further comprises determining a clock drift of the firstwireless node or the second wireless node.
 3. The asynchronous wirelesssystem of claim 1, wherein the synchronization of the first and secondwireless nodes occurs less frequently than determining a relative orabsolute position of the third wireless node.
 4. The asynchronouswireless system of claim 1, wherein the synchronization of the first andsecond wireless nodes comprises calculation methods to determineabsolute clock phase difference at time of synchronization and a rate ofchange of the absolute clock phase difference.
 5. The asynchronouswireless system of claim 1, wherein the first wireless node has a firstreference clock signal and the second wireless node has a secondreference clock signal.
 6. The asynchronous wireless system of claim 1,wherein the synchronization is performed on demand.
 7. The asynchronouswireless system of claim 1, further comprising: a fourth wireless nodeto send an initial communication to the third wireless node.
 8. Theasynchronous wireless system of claim 1, wherein the third wireless nodesends an initial communication to a fourth wireless node.
 9. Theasynchronous wireless system of claim 7, wherein a role of one of thefirst, second, or fourth wireless nodes is randomly or rotatablyselected.
 10. The asynchronous wireless system of claim 7, wherein arole of one of the first, second, or fourth wireless nodes is selectedbased on quality of wireless communications to other wireless nodes orlocation within the wireless network architecture.
 11. The asynchronouswireless system of claim 1, wherein TDoA ranging activity is used tocause synchronization when synchronization is needed.
 12. Theasynchronous wireless system of claim 1, further comprising: a fifthwireless node having an unknown location and including a wireless devicewith RF circuitry to enable communications with other wireless nodes inthe wireless network architecture, wherein the one or more processingunits of the first wireless node are configured to execute instructionsto receive a third communication from the fifth wireless node, todetermine time difference of arrival information of the reception of thefifth communication between each of the first and the second wirelessnodes, to determine ranging including a relative or absolute position ofthe fifth wireless node using the time difference of arrivalinformation.
 13. The asynchronous wireless system of claim 12, whereinpackets from the third and fifth wireless nodes are captured serially.14. The asynchronous wireless system of claim 1, further comprising: afifth wireless node having an unknown location and including a wirelessdevice with RF circuitry to enable communications with other wirelessnodes in the wireless network architecture, wherein packets from thethird and fifth wireless nodes are captured in parallel by using a firstRF channel to capture packets from the third wireless node and a seconddifferent RF channel to capture packets from the fifth wireless node.15. The asynchronous wireless system of claim 14, wherein the packetscaptured across the first and second RF channels are used to build acomprehensive location map of the third and fifth wireless nodessimultaneously, wherein packets from the third and fifth wireless nodesare captured in series during a first time period and in parallel duringa second time period depending on network conditions within the wirelessnetwork architecture.
 16. The asynchronous wireless system of claim 1,wherein one of the first and second wireless nodes is a third partydevice.
 17. The asynchronous wireless system of claim 1, wherein thefirst wireless node sends addressed synchronization packets to anchornodes individually or sends the synchronization packets with noaddressing to all anchor nodes.
 18. The asynchronous wireless system ofclaim 1, wherein the first wireless node sends a packet to the thirdwireless node and this packet is received by the second wireless nodeand used for synchronization, wherein this packet in combination withthe second wireless node receiving packets between the first wirelessnode and the third wireless node provides contention free transmissionand no overhead due to synchronization being performed with anacknowledgement packet.
 19. The asynchronous wireless system of claim 1,wherein the first wireless node and the third wireless node areconfigured to support fine time measurement (FTM) protocol and FTMpackets.
 20. A computer implemented method for localization of nodes ina wireless network architecture comprises: initializing the wirelessnetwork architecture having first and second wireless nodes with atleast one wireless node having a known location; receiving a firstcommunication from a third wireless node having an unknown location;determining time difference of arrival (TDoA) information upon receptionof the first communication between each of the first and the secondwireless nodes; determining TDoA ranging including a relative orabsolute position of the third wireless node using the time differenceof arrival information; sending a second communication with asynchronization packet that is received by the second wireless node; andsynchronizing the first and second wireless nodes based on the secondcommunication with the synchronization of the first and second wirelessnodes being decoupled from the first communication.
 21. Thecomputer-implemented method of claim 20 further comprising: determiningtransmission and reception timestamps of the second communication;determining channel state information of the synchronization packet tocalculate a distance between the first and second wireless nodes fromknown locations of the first and second wireless nodes, wherein thesynchronization of the first and second wireless nodes further comprisesdetermining a clock drift of the first wireless node or the secondwireless node.